JP4448433B2 - Manufacturing method of thermal head - Google Patents

Description

The present invention relates to a method for manufacturing a thermal head mounted on, for example, a thermal transfer printer.

  The thermal head has a heat storage layer made of a highly heat-insulating material such as glass, a plurality of heating resistors that generate heat when energized, and a group of individual electrodes that are individually connected to each heating resistor on a substrate with excellent heat dissipation. And a common electrode group that applies a common potential to all the heating resistors, and the heating resistor that has generated heat through the common electrode and the individual electrodes is pressed against the printed material wound around the ink ribbon and the platen roller. Printing operation. The common electrode and the individual electrode are generally connected to both ends in the resistance length direction of the heating resistor and arranged in a straight line in the resistance length direction, but the substrate size is reduced and the heating resistor is mounted on the substrate. In order to arrange it at the end of the substrate, a structure in which the common electrode is folded back has also been proposed. In this electrode folding structure, for example, one printing dot is constituted by two heating resistors whose one ends are connected by a conductor, and an individual electrode and the other heating resistor are formed at the other end of one heating resistor. A common electrode is connected to the other end of each.

  Such a thermal head can be formed by, for example, the following steps.

First, a resistor film is entirely formed on a substrate having a heat storage layer, and an insulating barrier layer that defines the resistance length of the heating resistor to be formed is formed on the resistor film. The region of the resistor film covered with the insulating barrier layer later becomes a plurality of heating resistors. When the insulating barrier layer is formed, a resist film is formed on the entire surface of the insulating barrier layer and the resistor film, and exposed and developed to form a resist pattern. As the resist film, a positive type is generally used, and the exposed portion of the resist film is dissolved by the developer. Subsequently, the resistor film exposed from the resist pattern is removed by, for example, etching, and the resist pattern is removed. After the resist pattern is removed, a conductor layer is formed on the entire surface of the exposed heat storage layer, resistor film, and insulating barrier layer. Subsequently, a part of the conductor layer is removed, a conductor for conductively connecting adjacent heating resistors, a common electrode group commonly connected to a plurality of heating resistors, and an individual electrode individually connected to each heating resistor Form a group. A pair of heating resistors connected by the conductor constitutes a printing dot, and the common electrode and the individual electrode are connected to the printing dot in the same direction. An electrode pad for bonding and connecting a plurality of drive ICs for controlling energization to the plurality of heating resistors on one end of each individual electrode (the end opposite to the side connected to the heating resistors) Form. The common electrode group and the individual electrode group are arranged at intervals for each of the plurality of small group electrode groups, and the drive IC is provided for each of the divided small group electrode groups, and each individual electrode belonging to the small group electrode group Selectively energize.
JP-A-8-127144 Japanese Patent Laid-Open No. 10-188395

  In the conventional structure described above, the resistor film is left in a solid shape in the dummy region sandwiched between adjacent small group electrode groups where the common electrode, the individual electrode, and the electrode pad do not exist. For this reason, during resist development, the developer wettability differs near the boundary between the actual area where the resist pattern is formed at a predetermined pitch interval and the dummy area where the resist film remains solid, and is formed near the dummy area. The resist pattern may be disturbed. If the shape and size of the heat generating resistor formed due to the disturbance of the resist pattern are deviated, the amount of heat generated by the heat generating resistor varies, resulting in uneven printing density, and the print quality deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to obtain a method for manufacturing a thermal head in which a resistor pattern shape is defined with high accuracy and print density unevenness can be suppressed.

  The present invention has been made in view of the fact that the heating resistor can be defined with high precision if the developer wettability is uniform during resist exposure and development when forming the heating resistor (resistor pattern). is there.

That is, the present invention prints via a print dot group arranged at a predetermined pitch, a common electrode group that applies a common potential to all print dots, an individual electrode group that is individually connected to each print dot, and each individual electrode. A drive IC for selectively energizing dots, the common electrode group and the individual electrode group are arranged at intervals for each of the plurality of small group electrode groups , and the drive IC is provided for each of the divided small group electrode groups. have been, the sandwiched by adjacent small group electrode group region, there a method of manufacturing a thermal head having a predetermined at a pitch interval, printing dots and the dummy resistor pattern of the non-connected to both of the drive IC Thus, a dummy resistor pattern is formed at the same time as the resistor pattern constituting the printing dots by using a photolithography technique .

It is practical that the common electrode group and the individual electrode group are stacked on the resistor pattern. The dummy resistor patterns are preferably formed at the same pitch interval as the minimum pitch interval of the common electrodes and individual electrodes belonging to the small group electrode group. For example, when the common electrode and the individual electrode are alternately arranged in the small group electrode group, the pitch interval between the common electrode and the individual electrode is the minimum pitch interval.

  The dummy resistor patterns are preferably arranged in parallel with the common electrodes and the individual electrodes, and can be arranged so as to have a symmetrical shape with respect to the center position between adjacent small group electrode groups.

  The printed dot has two heating resistors whose one ends are connected to each other by a conductor, and an individual electrode is connected to the other end of this one heating resistor, and the other end of the other heating resistor is common. It is practical that the electrodes are connected.

ADVANTAGE OF THE INVENTION According to this invention, the resistor pattern shape can be prescribed | regulated with high precision and the manufacturing method of the thermal head which can suppress printing density nonuniformity can be obtained.

  FIG. 1 is a schematic configuration diagram showing an overall configuration of a thermal head to which the present invention is applied, and FIGS. 2 and 3 are a schematic plan view and a schematic sectional view showing the configuration of the thermal head (excluding a protective layer).

The thermal head 1 has a heat storage layer 3 made of a heat insulating material such as glass on a substrate 2 made of Si, a ceramic material, a metal material or the like and excellent in heat dissipation, and on the heat storage layer 3, FIG. A plurality of heating resistors 4 arranged in a line at a minute interval in the left-right direction in FIG. 2 are provided. Each heating resistor 4 is a part of a resistor pattern 40 partially formed on the heat storage layer 3 using a cermet material such as Ta ₂ N or Ta—SiO ₂ , and the surface thereof is an insulating barrier layer. 5 is covered. The resistor pattern 40 exists in a region where a conductor (contact conductor 6, individual electrode 7, common electrode 8, and common line 9) is formed outside the region to be the heating resistor 4 (see FIG. 4). It functions as an adhesion layer that improves adhesion with the layer 3. The insulating barrier layer 5 is made of an insulating material such as SiO ₂ , SiON, or SiAlON, for example, and defines the planar size (length dimension L, width dimension W) of each heating resistor 4. Between adjacent heating resistors 4, there is a gap region α where the heat storage layer 3 is exposed. In the present embodiment, one printing dot D is formed by a pair of adjacent heating resistors 4 (4a, 4b), and the plurality of printing dots D are in a direction orthogonal to the energization direction of the heating resistor 4 (in FIG. 1). Arranged in the horizontal direction).

  As shown in FIG. 2, the pair of heating resistors 4a and 4b have one end in the resistance length direction and a gap between them covered with a rectangular contact conductor 6, and the resistance length of one heating resistor 4a. The individual electrode 7 is connected to the other end portion in the direction, and the common electrode 8 is connected to the other end portion of the other heating resistor 4b. The individual electrode 7 and the common electrode 8 are connected to the printing dot D in the same direction and are alternately arranged in the dot arrangement direction. A gap region α exists between the individual electrode 7 and the common electrode 8.

  The common electrode 8 is provided for every two adjacent printing dots D, and is connected to two adjacent heating resistors 4b, and is parallel to the resistance length direction of the heating resistor 4b from the U-shaped portion. It has a substantially Y-shape having a straight portion extending in a long direction. Each common electrode 8 is connected to the common line 9 at the end opposite to the heating resistor 4b side. The common line 9 extends in the dot arrangement direction and is commonly connected to the plurality of common electrodes 8, and is fed from both ends in the longitudinal direction (left and right direction in FIG. 1). Electric power from an external power source provided separately from the substrate 2 is supplied to all the printing dots D via the common line 9 and each common electrode 8. The contact conductor 6, the individual electrode 7, and the common electrode 8 of the present embodiment are formed by overlaying the end portions on the side of each heating resistor 4 on the insulating barrier layer 5. In FIG. 1, the common electrode 8 and the common line 9 are not shown.

  The individual electrode 7 is provided for each printing dot D, and an electrode pad 10 for wire bonding the drive IC 21 to the end opposite to the heating resistor 4a side is arranged in the arrangement direction of the printing dots D. Are alternately arranged in a staggered manner at a pitch interval wider than the pitch interval of the heat generating resistors 4 in a direction parallel to. The individual electrode 7 and the common electrode 8 are arranged at intervals for each of the plurality of small group electrode groups A (A1 to A4).

  The drive IC 21 is a switching element that switches between energization / non-energization of the plurality of heating resistors 4. The drive IC 21 is provided for each of the divided small group electrode groups A1 to A4 in a separate drive unit 20 from the substrate 2, and selects each individual electrode 7 belonging to the small group electrode groups A1 to A4. Energized. The pitch interval of the drive IC 21 corresponds to the pitch interval of the small group electrode groups A1 to A4. FIG. 1 shows the structure of the thermal head 1 in a simplified manner, and the wires connecting the actual electrode pads and the drive IC are provided at a very small interval of about 50 μm.

  The contact conductor 6, the individual electrode 7, the common electrode 8, and the common line 9 are formed on the resistor pattern 40 by a conductive material such as Al, Cr, Ti, Ni, and W, for example. Although not shown, a wear-resistant protective layer is formed on the insulating barrier layer 5, the contact conductor 6, the individual electrode 7, the common electrode 8, and the common line 9 to protect against contact with the platen roller. .

  In the thermal head 1 configured as described above, the pitch interval of the drive ICs 21 is narrower than the pitch interval in the dot arrangement direction of the print dots D composed of the pair of heating resistors 4a and 4b. A region sandwiched between the individual electrode 7 belonging to the small group electrode group A and the resistor pattern 40 formed under the common electrode 8 is generated. The region sandwiched between the adjacent small group electrode groups A is positioned between the heating resistor and the electrode pad in a direction orthogonal to the dot arrangement direction, and is not connected to both the printing dot D and the electrode pad 10. The dummy resistor pattern 41 is formed. 2 and 4, the dummy resistor pattern 41 is shown in a solid color.

  FIG. 4 is a plan view showing the resistor pattern 40 and the dummy resistor pattern 41. The dummy resistor pattern 41 is formed simultaneously with the resistor pattern 40 by patterning the resistor film formed on the entire surface of the heat storage layer 3 by photolithography, and the pattern accuracy of the resistor pattern 40 at the time of the formation. It has a function to improve. Specifically, the dummy resistor pattern 41 is arranged in parallel with the resistor pattern 40 and at the same pitch interval as the resistor pattern 40, and has a symmetrical shape with respect to the central position C between the adjacent small group electrode groups A. Yes. Hereinafter, the region where the resistor pattern 40 is formed is referred to as “real region (= small group electrode group A)”, and the region where the dummy resistor pattern 41 is formed is referred to as “dummy region”.

  Next, with reference to FIGS. 5 and 6, the manufacturing method of the thermal head 1 according to the present embodiment, particularly, the manufacturing process of the dummy resistor pattern 41 will be described.

First, as shown in FIG. 5, a resistor film 4 ′ made of a cermet material such as Ta ₂ N or Ta—SiO ₂ is formed on the entire surface of the substrate 2 having the heat storage layer 3. An insulating barrier layer 5 that defines the resistance length L of the heat generating resistor to be formed is formed on '. The region of the resistor film 4 ′ covered with the insulating barrier layer 5 later becomes a plurality of heating resistors 4.

  Next, as shown in FIG. 6, a resist film is formed on the entire surface of the resistor film 4 ′ including the insulating barrier layer 5, exposed and developed to form a resist pattern R. A positive type is generally used for the resist film, and the exposed portion of the resist film is dissolved by the developer. The resist pattern R is provided with an actual region forming slit group S1 corresponding to the gap region α between the adjacent heating resistors and between the common electrode and the individual electrode, and between the adjacent actual region forming slit group S1, the actual region forming slit group S1 is provided. A dummy region forming slit group S2 is provided which is parallel to the end slits of the region forming slit group S1 and has the same pitch interval. The resistance width W of the heating resistor to be formed is defined by the real region forming slit group S1. By providing the actual region forming slit group S1 and the dummy region forming slit group S2, the slits are uniformly formed in the entire resist film, so that the wettability of the developer for dissolving the resist film is substantially uniform throughout the resist film. Thus, a good resist pattern R with no size unevenness can be obtained.

  Subsequently, the resistor film exposed from the resist pattern R is removed by, for example, etching, and the resist pattern R is further removed. As a result, as shown in FIG. 4, the resistor pattern 40 remains in the real region, and the dummy resistor pattern 41 remains in the dummy region sandwiched between the real regions. As described above, since the resist pattern R serving as a mask at the time of etching has no size unevenness, the resistor pattern 40 can be formed with high accuracy. Through the steps so far, a plurality of heating resistors 4 covered with the insulating barrier layer 5 and having a predetermined planar size (resistance length L, resistance width W) are obtained.

  After the resistor pattern 40 is formed, a conductor film is entirely formed on the exposed heat storage layer 3, insulating barrier layer 5, resistor pattern 40, and dummy resistor pattern 41, and then a part of the conductor film is formed. Is removed by etching or the like, leaving only the conductor film positioned on the resistor pattern 40. As a result, the contact conductor 6 that conducts and connects adjacent heating resistors 4, the individual electrode 7 that is individually connected to each heating resistor 4, the common electrode 8 that is commonly connected to the plurality of heating resistors 4, and the common A common line 9 connected to the electrode 8 is obtained.

  Subsequently, an electrode pad 10 is formed at the end of each individual electrode 7 opposite to the side connected to the heating resistor 4, and the substrate surface excluding the electrode pad 10 (exposed heat storage layer 3, insulation) A wear-resistant protective layer that covers the barrier layer 5, the contact conductor 6, the individual electrode 7, the common electrode 8, and the common line 9) is formed. And the thermal head 1 shown in FIGS. 1-3 is obtained by wire-bonding the electrode pad 10 exposed from the wear-resistant protective layer and the drive IC 21 corresponding to the electrode pad 10.

  As described above, in the present embodiment, the resistor pattern 40 stacked on the adjacent small group electrode group A (more specifically, the individual electrode 7 and the common electrode 8 belonging to the small group electrode group A exists). Dummy resistor patterns 41 are provided at the same pitch intervals as the individual electrodes 7 (resistor patterns 40) in the dummy region sandwiched between the actual regions. Therefore, there is no difference in the wettability of the developer near the boundary between the real region and the dummy region during resist exposure and development when forming the resistor pattern 40, and the resist pattern R, and thus the resistor pattern 40 is It can be formed with a specified shape and size with high accuracy. As a result, the amount of heat generation (heat generation resistance value) at each printing dot D becomes substantially uniform, so that unevenness in printing density is suppressed satisfactorily and excellent printing quality is obtained.

  The dummy resistor pattern 41 is preferably formed in the entire dummy region at the same pitch interval as the resistor pattern 40 as in the present embodiment, but is formed at least near the boundary between the real region and the dummy region. The pitch interval may be within the allowable range if it is about twice the pitch interval of the resistor pattern 40. Specifically, for example, the vicinity of the boundary between the real region and the dummy region may be provided at the same pitch interval as the resistor pattern 40, and the pitch interval may be increased at the center side of the dummy region.

  In this embodiment, the drive IC 21 that is wire-bonded to the electrode pad 10 is mounted on the drive unit 20 that is separate from the substrate 2, but the electrode pad 10 and the drive IC 21 may be provided on the same substrate. Good.

  In the above description, the thermal head 1 having the folded structure in which the individual electrode 7 and the common electrode 8 are connected to the printing dot D in the same direction has been described. However, in the present invention, the individual electrode and the common electrode are in the resistance length direction of the heating resistor. It is also applicable to a linear structure type thermal head arranged in a straight line.

It is a schematic block diagram which shows the whole structure of the thermal head by this invention. It is a schematic plan view which shows the structure of the thermal head (except a protective layer). It is a schematic cross section which shows the structure by the side of the separate electrode of the thermal head (except a protective layer). It is a top view which shows a resistor pattern and a dummy resistor pattern. It is a top view which shows 1 process of the manufacturing process of the thermal head. It is sectional drawing which shows 1 process of the manufacturing process of the thermal head.

Explanation of symbols

1 Thermal Head 2 Substrate 3 Heat Storage Layer 4 Heating Resistor 4 ′ Resistor Film 5 Insulating Barrier Layer 6 Contact Conductor 7 Individual Electrode 8 Common Electrode 9 Common Line 10 Electrode Pad 20 Drive Unit 21 Drive IC
40 resistor pattern 41 dummy resistor pattern A (A1 to A4) small group electrode group C center position D between small group electrode groups print dot L resistance length R resist pattern S1 real area forming slit group S2 dummy area forming slit group W Resistance width α Gap region

Claims (6)

A group of printed dots arranged at a predetermined pitch, a group of common electrodes for applying a common potential to all the printed dots, a group of individual electrodes individually connected to each printed dot, and the print dots selectively through each individual electrode A drive IC that energizes,
  The common electrode group and the individual electrode group are arranged at intervals for each of a plurality of small group electrode groups, and the driving IC is provided for each of the divided small group electrode groups. In the sandwiched area, a method of manufacturing a thermal head having a dummy resistor pattern that is not connected to both the printing dot and the driving IC at a predetermined pitch interval,
  A method of manufacturing a thermal head, wherein the dummy resistor pattern is formed simultaneously with the resistor pattern constituting the printing dots by using a photolithography technique. The method for manufacturing a thermal head according to claim 1, wherein the common electrode group and the individual electrode group are stacked on the resistor pattern. 3. The method of manufacturing a thermal head according to claim 1, wherein the dummy resistor pattern is formed at the same pitch interval as the minimum pitch interval of the common electrode and the individual electrode belonging to the small group electrode group. . 4. The method of manufacturing a thermal head according to claim 1, wherein the dummy resistor pattern is arranged in parallel with the common electrode and the individual electrode belonging to the small group electrode group. 5. 5. The thermal head manufacturing method according to claim 1, wherein the dummy resistor pattern is formed in a symmetrical shape with respect to a center position between adjacent small group electrode groups. 6. In the manufacturing method of the thermal head according to any one of claims 1 to 5, the printing dot is formed by two heat generating resistors connected to each other one end by a conductor, and one of the heat generating resistors is formed. A method of manufacturing a thermal head, wherein the individual electrode is connected to the other end side, and the common electrode is connected to the other end side of the other heating resistor.

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